The present invention relates to a concentration measuring apparatus for measuring a concentration of a specific component in a solution with the use of a socalled biosensor, a test strip to be used in the concentration measuring apparatus, a biosensor system using the concentration measuring apparatus and the test strip, and a method for forming a terminal on the test strip. The solution to be measured is specifically humor, e.g., blood, blood plasma, urine, saliva, etc. Blood is particularly often used.
Measuring apparatuses using a so-called biosensor are now in practical use for quantitatively detecting a specific component in humors of living bodies such as blood, urine or the like. In the measuring apparatus of the type, a compact and disposable test strip is fitted as the biosensor, and for instance, blood is dropped on the test strip, thereby to measure a concentration of glucose, lactic acid, cholesterol or the like in the blood.
The aforementioned method and a structure of the test strip for the concentration measurement are disclosed, for example, in the published specification of Japanese Patent Laid-Open Publication No. 4-357452. The test strip of this prior art is constructed as shown in FIG. 33. Specifically, a conductive carbon paste or the like is screen printed on a sheet of a strip of an insulating base material 2 thereby to form terminals 3, 4 adjacent to each other at one end part in a longitudinal direction of the base material 2. The terminals 3, 4 are extended in the longitudinal direction to form a measuring electrode 5 and a counter electrode 6 facing the measuring electrode 5 at the other end part of the base material 2. An insulating layer is formed on the insulating base material except for portions on the terminals 3, 4, the measuring electrode 5, and the counter electrode 6. A reaction reagent (not shown) composed of an enzyme, a mediator, etc. corresponding to a component to be measured is applied on the measuring electrode 5 and the counter electrode 6. A cover 8 is fitted via a spacer 7 over the base material 2 except the terminals 3, 4. A test strip 1 of FIG. 34 is thus obtained. A projection 10 is formed so as to prevent the test strip 1 from being set to a measuring apparatus in a wrong direction.
As is revealed, e.g., in the prior art No. 4-357452, the test strip 1 is set to a measuring apparatus 20 by being inserted from the side of the terminals 3, 4 to a setting part 21 of a card-shaped measuring apparatus 20 as shown in FIG. 35. A display part 22 is provided at a surface of the measuring apparatus 20 to display measurement results. The setting part 21 of the conventional measuring apparatus 20 has a positive and a negative electrodes to be electrically connected to the terminals 3, 4 of the test strip 1 when the test strip 1 is set to the measuring apparatus 20.
After the test strip 1 is set to the measuring apparatus 20, as is clear from the same prior art No. 4-357452, for instance, blood is spotted on the other end part of the test strip 1, which is aspirated by a capillary action to a space 9 formed in the spacer 7, reaches the reaction agent applied on the measuring electrode 5 and counter electrode 6 and reacts with the reaction reagent. A voltage is impressed then to the terminals 3, 4 of the test strip 1 from the measuring apparatus 20, whereby a reaction product through a reaction with the enzyme is oxidized. A current generated in this oxidation is measured at the measuring apparatus 20. The measured oxidation current is converted to a concentration of the specific component to be measured.
The reaction reagent used is, e.g., one that includes glucose oxidase as the enzyme when glucose in the solution is to be measured, or that includes lactate oxidase, cholesterol oxidase when lactic acid, cholesterol in the solution is to be measured, as disclosed in a published specification of Japanese Patent Laid-Open No. 8-278276.
As is apparent from the above description, the test strip corresponding to each component to be measured can be obtained by replacing the enzyme contained in the reaction reagent without changing a basic of the test strip 1. In other words, the structure of test strips can be made common in various kinds of components to be measured, and the measuring apparatus and manufacturing facility for the test strips can be shared, with the effect of a cost reduction for manufacturing the measuring apparatus and test strips. Although it is ideal that the test strips for corresponding components are demanded the same degree, practically, test strips for glucose are required most, while those for lactic acid or cholesterol are less required. If the test strips are constituted in the same structure, in the aforementioned irregular demand, the test strip for the irregular demand can be obtained simply only by changing the reaction reagent.
However, if in the common structure of test strips, it becomes difficult to distinguish the test strips, for example, between glucose test strips and lactic acid test strips. It may happen that the lactic acid test strip is inadvertently set to the measuring apparatus even though a concentration of glucose is necessary. Thus, an incorrect result is obtained.
The present invention is devised to solve the above-described inconvenience and has for its object to provide a concentration measuring apparatus, a test strip for use in the measuring apparatus, a biosensor system, and a method for forming terminals on the test strip whereby a target component is measured with the test strip fit thereto.
In accomplishing these and other aspects, according to a first aspect of the present invention, there is provided a concentration measuring apparatus to which a test strip is set, the test strip including on a base material a reaction reagent which is to react with a liquid test sample, a positive terminal, and a negative terminal, the terminals electrically detecting a concentration of a specific component in the liquid test sample based on the reaction of the reaction reagent, the concentration measuring apparatus comprising a positive electrode and a negative electrode to be electrically connected respectively to the positive terminal and the negative terminal of the test strip, thereby operating the concentration of the specific component in the liquid test sample via the positive electrode and the negative electrode, the concentration measuring apparatus further comprising a type judgement electrode for judging a type of the test strip set to the concentration measuring apparatus with the type judgement electrode provided separately from the positive electrode and negative electrode.
As is fully described above, in the concentration measuring apparatus of the first aspect of the present invention, the type judgement electrode is added separately to the positive electrode and negative electrode. Thus, the specific component to be measured can be measured by the test strip which is appropriate to measure the specific component with the utilization of the type judgement electrode.
According to a second aspect of the present invention, the concentration measuring apparatus may further comprises a first identification device for feeding information corresponding to the test strip for the liquid test sample capable of measuring the specific component based on a fact that the type judgement electrode is connected with the positive electrode only when the test strip capable of measuring the specific component is set to the concentration measuring apparatus, and a second identification device for identifying the test strip based on the information fed from the first identification device.
According to the concentration measuring apparatus of the second aspect of the present invention, the first and second identification devices are provided further in the measuring apparatus of the first embodiment, which exhibits the following effects. When the test strip capable of measuring the component to be measured is set, the type judgement electrode and positive electrode are connected with each other, with information of the type of the set test strip being sent out from the first identification device. The second identification device recognizes based on the type information that an appropriate test strip to the measuring apparatus is set. The component to be measured can accordingly be measured by the appropriate test strip to the measuring apparatus.
According to a third aspect of the present invention, the concentration measuring apparatus may comprises switches for connecting or disconnecting the type judgement electrode and positive electrode, and for connecting or disconnecting the type judgement electrode and negative electrode, and an identification device for identifying that the test strip for the liquid test sample capable of measuring the specific component is set to the concentration measuring apparatus on the basis of information obtained from a detecting part of the positive electrode consequent to turning ON/OFF of each of switches.
According to the third aspect of the present invention, the concentration measuring apparatus of the first embodiment is further provided with the switches and the identification device, which exhibits the following effects. The identification device can judge whether or not the test strip conforming to the measuring apparatus is set based on the information of the detecting part of the positive electrode consequent to the turning ON/OFF of the switches. Therefore, the component to be measured can be measured by the appropriate test strip to the measuring apparatus.
According to a fourth aspect of the present invention, the concentration measuring apparatus may comprises a potential judge device connected to the type judgement electrode which judges whether or not the type judgement electrode becomes an appropriate test strip set potential which is a potential generated at the type judgement electrode when the test strip for the liquid test sample capable of measuring the specific component is set to the concentration measuring apparatus.
According to the fourth aspect of the present invention, the potential judge device is included in the concentration measuring apparatus of the first embodiment. The potential judge device detects the potential of the type judgement electrode thereby to judge whether or not the potential is the appropriate test strip set potential. When the potential is the appropriate test strip set potential, the potential judge device judges that the test strip fit to the concentration measuring apparatus is set.
Accordingly, the component to be measured can be measured by the test strip conforming to the measuring apparatus.
According to a fifth aspect of the present invention, the concentration measuring apparatus may comprises a change judge device connected to the type judgement electrode which judges whether or not a potential change at the type judgement electrode corresponds to an appropriate test strip set change which is a change generated at the type judgement electrode when the test strip for the liquid test sample capable of measuring the specific component is set to the concentration measuring apparatus.
The concentration measuring apparatus of the fifth aspect has the change judge device added to the concentration measuring apparatus of the first embodiment. More specifically, the change judge device detects the potential change at the type judgement electrode when the test strip is set to the measuring apparatus, thereby judging whether or not the potential change corresponds to the appropriate test strip set change. If the potential change is the appropriate test strip set change, the change judge device judges that the test strip suitable to the measuring apparatus is set. The component can hence be measured by the test strip matching the measuring apparatus.
According to a sixth aspect of the present invention, there is provided a test strip to be set to the concentration measuring apparatus in the second aspect of the present invention, which comprises a type judgement terminal which is to be electrically connected to the type judgement electrode and positive electrode, thereby letting the first identification device of the concentration measuring apparatus send out the information corresponding to the test strip for the liquid test sample capable of measuring the specific component.
According to the sixth aspect of the present invention, the test strip set to the concentration measuring apparatus of the second aspect has the type judgement terminal. Since the information that the test strip is fit to the measuring apparatus is sent out from the first identification device, the test strip enables the measuring apparatus to judge that the test strip appropriate to the measuring apparatus is set.
According to a seventh aspect of the present invention, there is provided a test strip to be set to the concentration measuring apparatus in the fourth aspect of the present invention, which is characterized by comprises a type judgement terminal which is to be electrically connected to the type judgement electrode and letting the potential judge device judge that the potential at the type judgement electrode is the appropriate test strip set potential.
In the seventh aspect of the present invention, the test strip is set to the concentration measuring apparatus of the fourth aspect, which is equipped with the type judgement terminal. The test strip enables the potential judge device to judge that the potential at the type judgement electrode is the appropriate test strip set potential. The test strip of the seventh aspect enables the measuring apparatus to judge that the appropriate test strip is set to the measuring apparatus.
According to a eighth aspect of the present invention, there is provided a test strip to be set to the concentration measuring apparatus in the fifth aspect of he present invention, which comprises type judgement terminal to be electrically connected to the type judgement electrode and letting the change judge device judge that the potential change at the type judgement electrode corresponds to the appropriate test strip set change.
According to the eighth aspect, the test strip is set to the measuring apparatus of the fifth aspect and equipped with the type judgement terminal. The change judge device can consequently judge that the potential of the type judgement electrode shows the change by an appropriate test strip. The test strip enables the measuring apparatus to judge that the appropriate test strip is set.
According to a ninth aspect of the present invention, there is provided a biosensor system which comprises
a first concentration measuring apparatus comprising the concentration measuring apparatus according to the second aspect wherein the positive electrode, the type judgement electrode, and the negative electrode are arranged in this order in a direction orthogonal to a set direction of a test strip;
a first test strip comprising the test strip according to the sixth aspect to be set to the first concentration measuring apparatus, which includes first terminals to be electrically connected to the positive electrode and the type judgement electrode, and a second terminal to be electrically connected to the negative electrode;
a second concentration measuring apparatus comprising the concentration measuring apparatus according to the second aspect wherein the positive electrode, the negative electrode, and the type judgement electrode are arranged in this order in the orthogonal direction; and
a second test strip comprising the test strip according to the sixth aspect to be set to the second concentration measuring apparatus which includes a first terminal to be electrically connected to the positive electrode and type judgement electrode and a second terminal to be electrically connected to the negative electrode,
said biosensor system so constituted that a concentration of the specific component cannot be operated if the first test strip is set to the second concentration measuring apparatus, and if the second test strip is set to the first concentration measuring apparatus.
The biosensor system in accordance with the ninth aspect of the present invention is constituted so that only one kind of the test strip conforms to one kind of the concentration measuring apparatus, making it impossible to share test strips and concentration measuring apparatuses among different kinds.
According to a tenth aspect of the present invention, in the concentration measuring apparatus of the fifth aspect, the change judge device may stores a plurality of calibration curve information for compensating for an error in concentration measurement of the specific component in the liquid test sample,
detects a calibration curve information selection change at the type judgement electrode so as to select a required calibration curve information among the plurality of calibration curve information in place of judging the presence/absence of the appropriate test strip set change at the type judgement electrode when the concentration measuring apparatus can measure the concentration of the only one specific component and the test strip having a reaction reagent which is to react to the specific component and capable of measuring the concentration of the specific component by the concentration measuring apparatus is set to the concentration measuring apparatus, and
compensates for the error based on the calibration curve information selected in accordance with the detected calibration curve information selection change.
According to the concentration measuring apparatus in the tenth aspect, the calibration curve information selection change is detected, instead of detecting the presence/absence of the appropriate test strip set change in the measuring apparatus of the fifth aspect. The calibration curve information can be selected on the basis of the above detection, and the measurement error can be compensated for by the selected calibration curve information. Accordingly, the concentration of the specific component can be obtained with higher accuracy.
According to a 11th aspect of the present invention, in the concentration measuring apparatus of the fifth aspect, the change judge device may stores a plurality of calibration curve information for compensating for an error in concentration measurement of the specific component in the liquid test sample,
selects a required calibration curve information among the plurality of calibration curve information on the basis of a calibration curve information selection change included in the appropriate test strip set change at the type judgement electrode as well as judges a type of the test strip on the basis of the appropriate test strip set change at the type judgement electrode, and
compensates for the error based on the selected calibration curve information.
According to the 11th aspect, in the concentration measuring apparatus of the fifth aspect, the calibration curve information selection change is detected in addition to the detection of the presence/absence of the appropriate test strip set change, whereby the calibration curve information corresponding to the detected type of the test strip set to the measuring apparatus and the production lot of the test strip can be selected.
According to a 12th aspect of the present invention, there is provided a test strip to be set to the concentration measuring apparatus of the 10th aspect, which has a type judgement terminal to be electrically connected to the type judgement electrode and letting the change judge device detect the calibration curve information selection change for selecting the required calibration curve information among the plurality of calibration curve information on the basis of the potential at the type judgement electrode.
According to the 12th aspect of the present invention, the test strip is set to the concentration measuring apparatus of the 10th aspect. The test strip is provided with the type judgement terminal for detecting the calibration curve information selection change, thus enabling the change judge device to select the calibration curve information.
According to a 13th aspect of the present invention, there is provided a test strip to be set to the concentration measuring apparatus of the 11th aspect, which has a type judgement terminal to be electrically connected to the type judgement electrode and letting the change judge device judge that the potential change at the type judgement electrode is the appropriate test strip set change for judging the type of the test strip and also letting the change judge device detect the calibration curve selection information change for selecting the required calibration curve information among the plurality of calibration curve information.
The test strip of the 13th aspect is set to the concentration measuring apparatus of the 10th aspect, which includes the type judgement terminal for detecting the calibration curve information selection change as well as the presence/absence of the appropriate test strip set change. Thus, the test strip of the 13th aspect enables the change judge device to judge the kind of the specific component measurable by the test strip set to the measuring apparatus and moreover, select the calibration curve information.
According to a 14th aspect of the present invention, there is provided a method for manufacturing the test strip of the 12th and 13th aspects, which comprises:
applying the reaction reagent on the base material of the test strip;
dropping a standard solution having the specific component of which a concentration is known to the applied reaction reagent;
selecting the calibration curve information compensating for an error between a detected concentration based on the reaction and the known concentration of the specific component; and
forming the type judgement terminal so that the calibration curve information selection change indicating at least the selected calibration curve information is generated at the type judgement terminal.
In the method for forming the terminals of the test strip according to the 14th aspect, after the calibration curve information is selected, the type judgement terminal is formed to the test strip of the 12th, 13th aspect so that the calibration curve information selection change is brought about.